Prefabricated floor boards provided with tongue and groove at the edges are quite common nowadays. These can be installed by the average handy man as they are very easy to install. Such floors can, for example, be constituted of solid wood, fiber board or particle board. These are most often provided with a surface layer such as lacquer, or some kind of laminate. The boards are most often installed by being glued via tongue and groove. The most common types of tongue and groove are however burdened with the disadvantage of forming gaps of varying width between the floor boards in cases where the installer has not been thorough. Dirt will easily collect in such gaps. Moisture will furthermore enter the gaps which will cause the core to expand in cases where it is made of wood, fiber board or particle board, which usually is the case. The expansion will cause the surface layer to rise closest to the edges of the joint which radically reduces the useful life of the floor since the surface layer will be exposed to exceptional wear. Different types of tensioning devices forcing the floor boards together during installation can be used to avoid such gaps. This operation is however more or less awkward. It is therefore desirable to achieve a joint which is self-guiding and thereby automatically finds the correct position. Such a joint would also be possible to utilize in floors where no glue is to be used.
Different types of joints with mechanical locking have been made available. One such joint is known through WO 94/26999. Here a lower lip is present in the form a thin strip which in selected embodiments is made of thin, aluminum sheets. This is a delicate part which is easily damaged when cutting the panel in connection to the assembly. The same problem applies to some extent on embodiments known through WO 97/47834. The locking parts of these types of floor panels are delicate and easily damaged but once properly installed are still very strong. It is an object of the present disclosure to solve the problem connected to the cutting and assembly of these and similar type of floor panels being provided with delicate locking parts.